1. Field of the Invention
The present invention relates to a soundproofing material. More specifically, the present invention relates to a soundproofing material which does not have a problem such as a reduction in area contributing to soundproofing as a result of an end portion and a periphery of a through hole for inserting various members being crushed and which is lightweight and has sufficient soundproofing performance.
2. Related Art
A sheet formed of an ethylene propylene diene rubber (EPDM) or the like has been conventionally used as a soundproofing material such as a dash silencer shown in FIG. 1 and a floor silencer for a vehicle. Although the sheet sufficiently functions as a sound isolating material, there has been a problem regarding weight. In addition, a soundproofing material has been known in which a soft material (corresponding to a spring) having low density and high air permeability and a hard material (corresponding to a mass) having high density and low air permeability are laminated to isolate and absorb sound generated from a vehicle body panel using a vibration-proof region of spring-mass resonance. This soundproofing material is lightweight and has excellent soundproofing performance.
Further, Japanese Unexamined Patent Application Publication No. 2004-237452 and the like disclose a composite member with noise preventing and impact absorbing performances in which one surface is closed, another surface is opened, and a fiber material with a specific thickness is compounded and installed on the open surface side of a plate-shaped molded honeycomb foam having a specific density. Additionally, Japanese Unexamined Patent Application Publication No. 2005-145383 and the lie disclose a vehicular interior member that has a specific structure and includes: an impact absorbing member having a plurality of openings penetrating to the back side and having a plurality of ribs on the back side; and a sound absorbing member formed of a material capable of absorbing noise and attached to the impact absorbing member from the back side.
In the above-mentioned soundproofing material in which the soft material and the hard material are laminated to isolate and absorb sound using a spring-mass effect, a stud bolt 4 installed in a vehicle body panel 204 is generally inserted to an attachment hole provided in the soundproofing material and fixed with a clip 5 at a vertical wall surface of a vehicle body, for example (see FIG. 9). In this case, the periphery of the attachment hole and an end portion of the soundproofing material are crushed to form a crushed portion 1′ in order to reduce leakage of sound from an end surface. However, when a felt or the like used as the soft material is crushed, there has been a problem that the proportion of area capable of exhibiting sufficient performance as the spring decreases, causing a decrease in the soundproofing performance. In addition, since the fiber material corresponding to the mass is fixed and does not vibrate in the case where the spring-mass effect is assumed in the composite member disclosed in Japanese Unexamined Patent Application Publication No. 2004-237452, the noise cannot be sufficiently blocked and absorbed. Further, since the vehicular interior member disclosed in Japanese Unexamined Patent Application Publication No. 2005-145383 does not have a member corresponding to the mass, the soundproofing member corresponding to the spring is fixed and does not vibrate, the noise cannot be sufficiently blocked and absorbed.